The present invention relates to a washing apparatus having a plurality of operative types of brushes. More particularly, the invention relates to an apparatus for washing semiconductor slices (wafers) and the like by using separately, for example, a nylon brush having hard "hairs" or stalks and a mohair brush having soft hairs.
Generally, wafers at the water process manufacturing stage, e.g., at the stage where they have just been sliced from a monocrystal silicon rod, are vigorously washed by a hard brush such as nylon brush with the distance between said brush and the wafer kept constant. On the other hand, at the stage where integrated circuits have been built into the wafers, they are gently washed by a soft brush such as mohair in such a manner that the brush is in contact with the wafer with a constant weight, (tens to hundreds of grams), applied to the brush while exercising care not to damage the integrated circuits.
Such, a conventional washing apparatus is shown in FIG. 1. In this figure, there are installed side by side a washing tank 3 for a wafer 2 used for initial washing of wafers and having a spin chuck in the middle, and a brush washing tank 5 which receives a nylon brush 1 therein when the wafer 2 is not being washed. In the brush washing tank 5, the brush 1 is washed with pure water spouting from a shower pipe 4. When the wafer 2 is handled and held on the spin chuck by suction, an air cylinder 8 is operated to advance a rack 9 interlocked to a pinion 7, so that a swing lever 1" fixed at one end to said pinion 7, and at the other end to a bearing supporting said brush 1, transfers the brush 1 onto the wafer 2. The wafer 2 is rotated by the spin chuck, while the brush 1 is rotated by a motor (not shown) through a belt 6. In this case, the brush 1 is forced into contact with the wafer 2 and the latter is washed as a result of the springback force of the hairs of the brush 1. The pressing force on the brush 1 is obtained by contacting the brush 1 and wafer 2 with each other when the air cylinder 8 is at the stroke end and hence when the brush 1 is at a certain level somewhat below its highest level.
Next, for the washing of the wafer 2 in the stage wherein integrated circuits have been built thereinto, in said apparatus the nylon brush 1 is replaced by a soft-hair mohair brush 1, and the wafer having the integrated circuit is washed in the same manner as before. In this case, the pressing force on the brush 1 is obtained by applying a load of tens to hundreds of grams to the brush, but it may be obtained by bringing the brush 1 and wafer 2 into contact with each other at a certain level somewhat below its highest level when the air cylinder is at the stroke end, as in the preceding case. However, as a result of this operation distance between the brush 1 and the wafer 2 is always constant so that even if the brush 1 uses a soft material there is a drawback that there is no play in the brush position, thus making gentle washing impossible.
Accordingly, the present invention has as an object to eliminate the drawback of the prior art and is intended to improve on the conventional washing apparatus and to provide a washing apparatus capable of using a plurality of types of brushes each in its optimum operational condition.